Introduction to File Handling

Introduction to File Handling

File handling allows programs to store and retrieve data persistently by reading from and writing to files.

In this lesson, you will learn:

• How to open and close files in C.
• How to read and write data using file handling functions.
• The importance of file operations in real-world applications.

Files in C are opened using the fopen() function.

Syntax:

FILE *filePtr = fopen("filename.txt", "mode");

Modes:

• r - Read
• w - Write
• a - Append

Files should be closed using the fclose() function to free resources.

Example:

fclose(filePtr);

Failing to close files may cause memory leaks or file corruption.

The fprintf() function writes formatted data to a file.

Example:

fprintf(filePtr, "Hello, World!\n");

This writes Hello, World! to the file.

This program demonstrates how to write to a file.

#include <stdio.h>

int main() {
    FILE *filePtr = fopen("output.txt", "w");
    if (filePtr == NULL) {
        printf("Error opening file!\n");
        return 1;
    }
    fprintf(filePtr, "Hello, File Handling in C!\n");
    fclose(filePtr);
    return 0;
}

The fscanf() function reads formatted data from a file.

Example:

fscanf(filePtr, "%s", str);

This reads a string from the file into str.

This program demonstrates how to read data from a file.

#include <stdio.h>

int main() {
    FILE *filePtr = fopen("output.txt", "r");
    if (filePtr == NULL) {
        printf("Error opening file!\n");
        return 1;
    }
    char str[50];
    fscanf(filePtr, "%s", str);
    printf("File Content: %s\n", str);
    fclose(filePtr);
    return 0;
}

The a mode appends data to an existing file.

Example:

FILE *filePtr = fopen("data.txt", "a");

This opens data.txt for appending new content.

In this lesson, you learned:

• How to open and close files.
• How to write and read data using fprintf and fscanf.
• How to append data to an existing file.

Next, we will explore working with binary files in C!